The invention relates to a latent heat storage means adapted to store heat from the radiator of a motor vehicle in which it is mounted so that the radiator water may flow along a flow path and an with enclosure, separated from the latter by a heat exchanger surface, for the heat exchange medium.
A proposal has already been made to store the waste heat of IC engines in motor vehicles in heat storage means so that thermal energy is available for defrosting, for heating the driver's cab or car interior and/or heating up the engine and thus increasing the comfort of the driver and the working life of the engine. Furthermore, the fuel consumption and the emission of pollutants may both be reduced.
In the case of application to private cars it is more particularly necessary for the space requirement and the weight to be taken into account. Owing to the high storage capacity for a relatively low overall size the use of latent heat storage means is looked upon as being highly suitable for private cars.
As regards the selection of the heat storage medium care must be taken to see that the phase transition temperature comes within the desired range and it may be subjected without decomposition to the maximum temperature of the heat vehicle, in this case the radiator water. Furthermore it has to have a sufficient energy storage density in terms of the volume and mass. Materials which have an aggressive effect on the materials used for the construction of the storage means are unsuitable for heat storage.
So far materials suggested for use in automobiles and capable of yielding satisfactory results have been inorganic materials such as sodium hydroxide, in which case it is then necessary to use a material resistant, such as stainless steel, to the medium for containing it. Aluminum, which would otherwise be advantageous for the housing, may not be utilized, since it is attacked by the storage medium.
If water is used for charging the heat storage means, it is not possible to fully exclude the possibility of storage medium making its way into the radiator cooling circuit owing to leaks. Even indirect charging of the heat storage means via a secondary circuit heated by a heat exchanger is not able to fully eliminate this danger, apart from the fact the space requirement, the weight and the costs of the secondary circuit are a disadvantage.
In view of the ever increasing use of light metal alloys for the construction of modern engines it is necessary to exclude any possibility of corrosive materials, more particularly those which would attack aluminum, silicon and alloys thereof, finding their way into the cooling water cooling circuit.